The government has spent 20 times more subsidising the coal industry over the past six years than it has put into marine energy, new figures show.

Ministers have given away £52.8m of a £60m coal investment aid scheme to extend operations at a range of mines around Britain, including Daw Mill in Warwickshire where energy minister Mike O'Brien is the local MP. This contrasts with the £2.3m handed out from a £50m pot created under the Marine Renewables Deployment Fund, which started in 2004 just 12 months after the launch of the latest coal scheme.

"At a time when we need to deliver a major expansion in renewable energy, it's astonishing to find that less than 5% of the investment promised to give Britain a lead in marine energy has actually been made," said Greg Clark, shadow energy and climate change secretary.

"It is little wonder that Britain punches way below its weight on renewables - we have the third-lowest contribution from renewable energy in Europe, despite some of the best resources."

The Observer revealed last month that ministers had spent almost nothing out of the Marine Renewables Deployment Fund, with potential users complaining the conditions attached to grants were so onerous that they could not gain access.

The amount of cash handed out under the coal aid scheme was recently revealed in parliament and the Conservatives say that all of it - bar one grant - has been spent in Labour constituencies.

The government has sought to make up lost ground, with money being promised in the recent energy white paper to various tidal and other schemes. More than £20m has been earmarked for a new Marine Renewables Proving Fund with a further £9.5m going to develop a Wave Hub off Cornwall and £8m for a European Marine Energy Centre in Orkney.

But the Tories argue that ministerial promises mean very little. "It is easy to talk about support for renewables but what we need is action," said a spokeswoman. The opposition says it would use the money from the Marine Renewables Deployment Fund to establish a network of large-scale marine energy parks to be run on a commercial basis.

When the coal subsidies were launched in 2003 by the then trade and industry secretary, Patricia Hewitt, the main emphasis was on job retention.

Last night a spokesman for the Department of Energy and Climate Change said it was not helpful to compare two completely different technologies - coal having been in development for generations, and marine very much cutting edge.

He added: "We want to be a global leader in wave and tidal energy, that's why we announced £60m of low carbon investment funding in the budget. That included £22m to help pre-commercial testing of marine technology, which should enable access to the Marine Renewables Deployment Fund."